Canceling Out Cancer

Melanoma is a cancer of melanocytes, the cells which produce melanin and give color to the skin, hair, and other tissues. Over 8,000 people die of melanoma each year. Although canine melanoma deaths are not tracked, approximately 50,000 dogs in the U.S. develop melanoma annually. Traditional treatment for melanoma involves surgery often followed by radiation therapy and/or chemotherapy.

Melanoma can occur on many parts of the body, oral melanomas, the most common oral cancer in dogs, are especially aggressive and readily spread to the lymph nodes, liver, lungs, and kidneys. Average survival times for dogs with oral melanoma treated by surgery alone is three to six months depending on the stage of the disease at the time of treatment. There is little evidence that chemotherapy is effective in treating melanomas.

One difficulty with managing cancers is that the body’s immune system does not recognize the tumor as a foreign invader and does not respond to attack the abnormal cells. A recent research partnership between a group of veterinary cancer specialists and human oncologists at Memorial Sloan-Kettering Cancer Center has resulted in a new approach to cancer therapy. Their investigations have led to the development of a canine melanoma vaccine. We normally think of vaccines as a way to prevent disease, but this vaccine uses immunotherapy to treat canine melanoma.

The canine melanoma vaccine stimulates the body’s immune system to produce an immune response against tyrosinase, a chemical which is highly concentrated in melanoma cancer cells. This immune response specifically targets and attacks the melanoma cells.

The vaccine has been amazingly successful in the studies. Dogs treated with surgery alone had survival times of less than five to six months. In the group of dogs treated with surgery followed by the canine melanoma vaccine, more than 60 percent of the dogs were still alive three years later. In the vaccinated group, there was no difference in survival times based on stage of the tumor or completeness of the surgical removal. To date, more than 6,500 dogs with melanoma have been treated with the vaccine.

A really exciting next step in this research will be to try to identify genetic markers that make an individual dog more likely to develop melanoma and then use the vaccine to actually prevent the cancer. Taking this a step further, imagine how fantastic it would be to be able to translate this concept to human patients where we could identify individuals who had a genetic predisposition to say, breast cancer, and provide them with a vaccine to prevent the tumors from ever developing. The scientific discovery of this impressive new cancer therapy is an example of developments in the veterinary field that may have incredible potential in human medicine.